640908 has 36 divisors (see below), whose sum is σ = 1707160. Its totient is φ = 202176.

The previous prime is 640907. The next prime is 640919. The reversal of 640908 is 809046.

640908 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a tau number, because it is divible by the number of its divisors (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640901) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 216 + ... + 1152.

2⁶⁴⁰⁹⁰⁸ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 640908, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (853580).

640908 is an abundant number, since it is smaller than the sum of its proper divisors (1066252).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

640908 is a wasteful number, since it uses less digits than its factorization.

640908 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 966 (or 961 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The square root of 640908 is about 800.5672988575. The cubic root of 640908 is about 86.2181230658.

The spelling of 640908 in words is "six hundred forty thousand, nine hundred eight".